RAGLAND, GJ; KINGSOLVER, JG; University of North Carolina at Chapel Hill; University of North Carolina at Chapel Hill: Interaction of thermal biology and diapause timing in pitcher plant mosquitoes

In temperate, seasonal environments the occurrence of a dormant life history stage is generally believed to be a consequence of limits to thermal tolerance and/or performance: that is, dormancy evolves as an avoidance response to harsh temperatures that are deleterious to actively growing individuals. It is surprising, then, that with a few notable exceptions the specific relationship between thermal physiology and timing of dormancy has rarely been explored. Here I investigate the relationship between thermal performance and timing of diapause (the dormant life history stage in insects) in several geographic populations of the pitcher plant mosquito, Wyeomyia smithii, focusing specifically on diapause termination. The timing of photoperiod-induced diapause (the critical photoperiod, or CP) has been well characterized for this species across a broad range of geographic populations. Using these published estimates of CP I analyzed 50-year weather data and field measurements of pitcher plant fluid temperatures in order to characterize the thermal environment experienced near the CP for diapause termination. I use these data in conjunction with measures of the lower thermal threshold for development to determine whether (and how accurately) developmental parameters do in fact predict the timing of diapause termination given the native thermal environment of a population.